Articles and instruments for use in surgical and other medical procedures must be enclosed in a bacteria-inpervious and sterilized environment so that they will remain free of bacteria until they are needed. Surgical packages are therefore conventionally made of materials that are generally impervious to bacteria. These packages must also be designed so that they may be readily and rapidly opened without affecting the sterility of the contents and so that the contents may be removed from the package according to approved sterile techniques. It is conventional in such packages to provide tear strip openings for permitting access to the contents. The tear strips have generally been formed by scoring the exterior and interior surfaces of the paperboard to define planes of cleaveage therein along which the tear strips delaminate. In the past, at least two problems have been encountered with such package openings. First, where the packages are formed with glued manufacturers joints, the starting end of the tear strip which is pulled upon to open the packages is generally adhesively bonded to the paperboard in the region of the manufacturers joint, and these tear strip arrangements frequently malfunction by either not delaminating at all or by delaminating along planes other than those defined by the tear strip scores at the interior and exterior surfaces of the paperboard. The improper delamination of the tear strips is caused by the fact that the adhesive bond between the manufacturers joint and the starting end of the tear strip, and the package, is stronger than the bond between the plies of delaminatable paperboard material from which the package is made. In those packages which are formed from blanks having heat sealable barrier coatings, a similar problem occurs because the barrier films are very tough and very difficult to tear, thus making it even more difficult to initiate the opening of the tear strip feature. A second problem that occurs with the packages of the prior art having conventional tear strip openings, is that once the tear strip is removed from the tear strip area, the contents of the package are immediately exposed to bacteria through the tear strip opening. Similarly, in the packages of the prior art, the paperboard surfaces which remain adjacent the access opening when the tear strip is removed provide a hostile environment for the contents of the package as they are removed from the package.
Several prior U.S. patents have attempted to overcome the problems noted above as described hereinafter. In U.S. Pat. No. 3,727,750, to Petter, a sterile package is disclosed having a removable tear strip which includes an intricate folded over tab formed on one end of the tear strip and a carefully defined plane of cleaveage along which the tear strip may be initially delaminated to insure a positive opening. However, once the tear strip of the Petter patent is removed, the contents of the sterile package are immediately exposed to bacteria and the design of the tear strip is such that only a minimal amount of protection is provided adjacent the edges of the access opening to protect the contents from being further contaminated as they are withdrawn from the package.
In a second U.S. Pat. No. 3,853,261, to Moore, another sterile package is disclosed that is formed from a blank of paperboard coated on at least one surface with a heat sealable barrier film such as polyethylene or the like. In this latter patent limited depth cuts are formed in the exterior surface of the carton blank in the area under the tear strip in the region of the manufacturers flap to permit delamination of the paperboard material when the tear strip is initially torn. However, as in the case of the Petter invention, the Moore patent also exposes the contents of the package to bacteria as soon as the tear strip is removed. Moreover, because the Moore package is comprised of a blank having a heat sealable barrier film the carton is sealed closed at the manufacturers flap by a heat sealing process and this process tends to adhere the tear strip to the manufacturers flap with considerable tenacity. Therefore the limited depth cuts in the exterior surface of the carton blank in the area under the tear strip of the Moore carton are not always sufficient to insure a proper opening every time.
In a third U.S. Pat. No. 3,495,702, to Kuster, a surgical package is disclosed which also incorporates a removable tear strip. Further, in one of the embodiments of the Kuster invention a sheet of relatively thin and flexible material underlies a paperboard panel in the area of the tear strip. The sheet of material is sealed to both the tear strip itself and the paperboard panel on each side of the tear strip. Thus, when the tear strip of Kuster is removed, the sheet of material underlying the paperboard panel is also torn, since it is sealed to the tear strip, and the simultaneous removal of the tear strip and that portion of the underlying sheet material that is adhered thereto creates a gap which exposes the contents of the carton to bacteria simultaneously with the removal of the tear strip.
On the other hand, the Kuster package is designed to hopefully leave two outward faces of the sheet of relatively thin and flexible material adjacent the access opening as the tear strip is removed to prevent further contamination of the contents of the carton as they are removed from the package.